P7- Radioactivity

Question 1

What is the mass number?

Answer 1

number of protons and neutrons

Question 2

What is the atomic number?

Answer 2

number of protons

Question 3

What is a isotope?

Answer 3

an element with a different number of neutrons

-e.g. oxygen-18

Question 4

Elements and isotopes?

Answer 4

all elements form isotopes, usually one or two stable ones.

Question 5

What happens to unstable isotopes?

Answer 5

unstable isotopes decay into other elements and emit alpha, beta or gamma radiation.

or they can release neutrons in the nucleus to try to balance the atomic number and mass number

Question 6

What is ionising radiation?

Answer 6

radiation that knocks electrons out of their orbit forming positive ions

Question 7

Describe alpha radiation:

Answer 7

• alpha particles emitted from the nucleus
• 2 protons and 2 neutrons (structure of helium)
• highly ionising
• can travel a few cm in air before being absorbed
• absorbed by paper

Question 8

Describe beta particles:

Answer 8

• beta particles are fast moving electrons released from nucleus
• virtually no mass charge -1
• moderately ionising
• can be absorbed with a few cm of aluminium
• can travel a few metres in air

Question 9

Describe gamma particles:

Answer 9

• em waves with short wavelengths
• absorbed by concrete or thick lead
• can penetrate for long distances without being absorbed
• weak ionising, collide with other atoms

Question 10

What is half life?

Answer 10

the amount of time is takes half the nuclei of an isotope sample to decay
or number of counts to half

Question 11

What does a short half life mean?

Answer 11

activity falls quickly so it’s very unstable and rapidly decays

Question 12

Activity of a sample of gold is 460. What is the final activity after 2 half lives

Answer 12

460/2= 230
230/2 = 115

Question 13

What’s background radiation?

Answer 13

low level radiation that’s always around us

comes from:

• natural occurring isotopes- food, air, rocks
• space- cosmic rays
• human activity: nuclear waste

Question 14

What is radiation dose and what is it measured in?

Answer 14

radiation dose is the risk of harm to body tissues due to the exposure of radiation
measured in Sieverts or milisieverts
1 Sv- 1000 mSv

Question 15

What is irradiation?

How can it be prevented?

Answer 15

• exposure to radioactive sources
• won’t make you radioactive
• keeping radioactive sources in a lead covered box
• standing in another room or behind boxes

Question 16

What is contamination?

How can it be prevented?

Answer 16

• radioactive particles getting onto objects
• radio active particles can decay and release radiation which is harmful as particles can get into your body

-gloves and protective tongs

Question 17

What are the issues with radiation?

Answer 17

can enter living cells and ionise atoms- causing tissue damage

lower doses- cause minor damage (don’t kill) but cause mutations which divide- cancer

high doses- kill cells which can cause radiation illnesses which results in vomiting